Subsurface pump and method

ABSTRACT

A subsurface pump and pumping method particularly for use in gassy oil wells to improve pumping efficiency and avoid gaslocks. A body of relatively gas-free fluid is trapped during each upstroke of the pump plunger. Gassy fluid coming directly from the well blends with this body to produce a blended fluid having a lower proportion of gas. The plunger encounters the blended fluid on its downstroke.

United States Patent Glen L. Hillis Gainesville, Tex.

Jan. 8, 1970 July 20, 1971 United States Steel Corporation Inventor Appl. No. Filed Patented Assignee SUBSURFACE PUMP AND METHOD 3 Claims, 3 Drawing Figs.

U.S. Cl 417/435, 166/1055,166/105.6,4l7/448,417/554 Int. Cl. ..1-04b 21/08,

F04b 47/00, E21 b 43/00 Field of Search 417/435, 448, 554, 523; lee/105.5, 105.6

i/fr l l [56] References Cited UNITED STATES PATENTS 3,148,629 9/1964 Sutliff 417/554 X 3,212,444 10/1965 Wells 417/448 X 3,479,958 11/1969 Anderson et a1 417/554 Primary Examiner-Leonard H. Gerin Attorney-Walter P. Wood ABSTRACT: A subsurface pump and pumping method particularly for use in gassy oil wells to improve pumping efflciency and avoid gaslocks. A body of relatively gas-free fluid is trapped during each upstroke of the pump plunger. Gassy fluid coming directly from the well blends with this body to produce a blended fluid having a lower proportion of gas. The plunger encounters the blended fluid on its downstroke.

SUBSURFACE PUMP AND METHOD This invention relates to an improved subsurface pump for use in oil wells and to an improved pumping method.

Some oil wells produce large volumes of gas as well as oil. When a conventional subsurface pump is used in such wells, the gas interferes with pumping efficiency. The pump plunger draws a large proportion of gas into the pump barrel during its upstroke. A substantial length of the ensuing downstroke is consumed merely in compressing this gas. Consequently the pump brings to'thesurface a smaller volumcof oil than should be expected for a trumpet its diameter and stroke length. In fact, the gas volume sometimes is so large that no oil reaches the surface, a condition known as a gaslock.

An object of the present invention is to provide an improved subsurface pump and pumping method which are more elfcient in gassy oil wells.

, A more specific object is to provide an improved pump and method in which gassy fluid drawn into the pump barrel during each upstroke of the plunger blends with a body of relatively gas-free fluid before the start of the ensuing downstroke, thereby lowering the proportion of gas in the fluid the plunger encounters during its downstroke.

In the drawing:

FIG. 1 is a diagrammatic vertical sectional view of a pump constructed in accordance with my invention showing the parts in the positions they occupy near the bottom of a downstroke;

' FIG. 2 is a similar view, but showing the parts at the midportion of an upstroke; and 1 FIG. 3 is another similar view, but showing the parts near the top of an upstroke.

My subsurface 'pump comprises lower and upper barrels l and 12, a tube 13 connecting the barrels end-to-end, and a hollow' plunger 14 movable through upstrokes and downstrokes within the barrels and tube. A rod string 15 is joined to the top .of the plunger and extends to a suitable pumping unit at the surface for driving the pump. The pump has standing and traveling valves 16 and 17 mounted respectively at the lower end of the lower barrel to and at the lower end of plunger 14. The upper ends of the upper barrel l2 and of plunger I4 have ports 18 and 19 respectively. The two barrels l0 and 12 are of the same inside diameter, and the connecting tube 13 is of larger inside diameter than the barrels.

Plunger 14 is longer than the connecting tube 13, whereby in its midposition it extends into both barrels I0 and 12 (FIG. 2). I can manufacture the pump of parts which per se are conventional and commercially available; hence I have shown the parts only diagrammatically.

During a downstroke (FIG. 1) the standing valve 16 closes and traveling valve 17 opens, as in conventional pump operation. Fluid, which was drawn into the lower barrel to during the preceding upstroke, enters plunger 14 through the traveling valve and flows out ports 19. During the final portion of each downstroke such fluid accumulates in the enlarged chamber within the connecting tube 13, where it is subject to the static pressure of the fluid column above the pump. Most free gas escapes upwardly.

During the ensuing upstroke (FIGS. 2 and 3) the standing valve 16 opens and the traveling valve 17 closes. The lower barrel I0 is under partial vacuum, whereby fluid from the well is drawn into the lower barrel through the standing valve. If

there is gas present, turbulence and low pressure tend to expand the gas and separate it from the liquid. Gas collects at the top of the lower barrel and liquid at the bottom. At the same time fluid which entered the plunger during preceding downstrokes is lifted toward the surface through ports 18.

At the midportion of the upstroke (FIG. 2) the lower end of the plunger is still within the lower barrel while the upper end of the plunger already has entered the upper barrel 12. Thus the body of fluid within the connecting tube 13 is trapped. The trapped fluid remains under pressure and relatively gas free. After the'lower end of plunger 14 emerges from the lower bar- -rel 10, near the conclusion of the upstroke, the lower barrel is open to the connecting tube 13. Fluid in the barrel blends with fluid in the tube. The proportion of gas in the blended fluid thus is lower than in fluid coming directly from the well as it enters the lower barrel. Any gas present rises to the top of the connecting tube.

When plunger 14. starts down, gas in the connecting tube 13 is subject to the pressure of the descending plunger, and does not ordinarily go back into solution. When this gas is compressed to the pressure above the traveling valve 17, the valve opens and permits fluid to flow up through the plunger. Since the proportion of gas in the blended fluid is lower than in fluid as it comes from the well, the descending plunger encounters liquid sooner than otherwise. At the midportion of the downstroke fluid within the connecting tube 13 again is trapped, although now there may be some free gas trapped within the tube. When the upper end of the plunger emerges from the upper barrel 12 (FIG. I), such gas escapes upwardly, as already pointed out.

From the foregoing description it is seen that my pump and pumping method produce during each cycle a blend of relatively gas free fluid and fluid which may contain gas. In this way the proportion of gas is lowered in the fluid which the descending plunger encounters. Thus pumping efficiency increases, and gaslocks are avoided.

-. I claim:

1. In a subsurface pump which includes at least one barrel, a hollow plunger movable through upstrokes and downstrokes within said barrel, a standing valve mounted on said barrel, and a traveling valve mounted on said plunger, the improvement comprising means connected with said barrel for forming a trapped relatively gas free body of fluid during upstrokes of said plunger and blending fluid from said barrel with said body near the conclusion of each upstroke, whereby said plunger encounters the blended fluid on its downstrokes.

2. A pump as defined in claim 1 in which said means comprises an upper barrel spaced above said first-named barrel and a connecting tube joining said barrels end-to-cnd and being of larger inside diameter than said barrels, said plunger being longer than said connecting tube, said body being formed within said connecting tube.

3. A method of pumping fluid from a gassy oil well comprising operating a subsurface pump within the well'through upstrokes and downstrokes of its plunger, drawing gassy fluid from the well into the pump during each upstroke, forming a trapped body of relatively gas free fluid within the pump at the midportion of each upstroke, blending said gassy fluid with said body near the conclusion of each upstroke to produce blended fluid having a lower proportion of gas than said gassy fluid, and encountering the blended fluid with the plunger at the beginning of each downstroke. 

1. In a subsurface pump which includes at least one barrel, a hollow plunger movable through upstrokes and downstrokes within said barrel, a standing valve mounted on said barrel, and a traveling valve mounted on said plunger, the improvement comprising means connected with said barrel for forming a trapped relatively gas free body of fluid during upstrokes of said plunger and blending fluid from said barrel with said body near the conclusion of each upstroke, whereby said plunger encounters the blended fluid on its downstrokes.
 2. A pump as defined in claim 1 in which said means comprises an upper barrel spaced above said first-named barrel and a connecting tube joining said barrels end-to-end and being of larger inside diameter than said barrels, said plunger being longer than said connecting tube, said body being formed within said connecting tube.
 3. A method of pumping fluid from a gassy oil well comprising operating a subsurface pump within the well through upstrokes and downstrokes of its plunger, drawing gassy fluid from the well into the pump during each upstroke, forming a trapped body of relatively gas free fluid within the pump at the midportion of each upstroke, blending said gassy fluid with said body near the conclusion of each upstroke to produce blended fluid having a lower proportion of gas than said gassy fluid, and encountering the blended fluid with the plunger at the beginning of each downstroke. 